Bandgap engineering for phononic crystals adjustment and applications

This review focuses on cutting-edge research directions in phononic crystals (PnCs), such as bandgap broadening and bandgap tunability. By elucidating the underlying physical mechanisms, it systematically compares the acoustic performance of different structural configurations. Furthermore, it explores in depth the application potential and specific case studies of such materials in fields including marine engineering. The core advantage of PnCs stems from their artificially engineered sub-wavelength structures, which enable anomalous modulation of constitutive parameters such as effective mass density and elastic modulus. This allows for precise acoustic impedance matching or mismatching, thereby efficiently controlling sound wave propagation paths and energy dissipation. Research indicates that the advancement of PnCs will significantly expand the technical approaches for ship vibration and noise reduction. Notably, with the deep integration of smart materials and digital design, PnCs are gradually evolving from static, passive structural units into dynamic, adaptive, and even intelligent acoustic processing systems. This trend not only provides transformative solutions to the long-standing challenges of low-frequency and ultra-low-frequency noise control but also heralds a new paradigm for acoustic-vibration environment regulation. In the future, major equipment and quiet spaces are expected to achieve active, precise, and programmable management of the acoustic-vibration environment, with a control logic analogous to that of electromagnetic spectrum regulation.